In recent years, the development of OLED display panels is progressing with the goal of achieving thinness, high luminosity and high speed of the display panel. These OLED display panels are provided from at least three organic light emitting diodes (OLED element) in which each pixel emits light in three primary colors (red, green, blue) respectively, response speed is fast due to the lack of mechanical operations, and in addition to high luminosity display being possible due to each pixel itself emitting light, next generation display panels are being expected since thinness is possible due to backlights becoming unnecessary.
Although these OLED display panels generally include a structure in which a plurality of OLED elements corresponding to each pixel of an image to be displayed are provided in a matrix on one substrate (glass substrate), in a so called top emission type panel, a transparent opposing substrate for preventing external light from entering is further bonded on an OLED element. Each OLED element in a top emission type panel is comprised from a TFT (Thin Film Transistor) drive circuit layer, a reflectance electrode layer (anode), a hole injection layer, a hole transport layer, an organic EL (Electro Luminescence) light emitting layer, an electron transport layer, an electron injection layer and a transparent electrode layer (cathode) in sequence from the substrate side. Furthermore, because the transparent electrode layer (cathode) is one sheet of transparent conductive material common to all the OLED elements, the transparent electrode layer is provided across the entire region of the display area (area in which an OLED element is provided) 101 shown in FIG. 12.
Although the transparent electrode layer is provided on a different layer to the TFT drive circuit provided on a substrate in the stacked structure described above, because a drive circuit for driving each OLED element or an element for supplying external drive power or an external drive signal to the drive circuit or connecting to ground is provided on the substrate, it is necessary to form a cathode contact 100 at a plurality of locations passing from the wiring on the substrate through to the layer in which the transparent electrode is provided as is shown in FIG. 12, make an earth wire provided on the substrate to conduct with the cathode contact 100 and connect the transparent electrode to each cathode contact 100.
Since the conducting material which forms the transparent electrode layer has a high resistance value, there is a larger drop in voltage from the wiring itself and a smaller potential difference with the cathode electrode the larger the gap between the transparent electrode and the cathode electrode 100 thereby a problem occurs wherein the amount of light emitted from an OLED element decreases (shedding).
Although arranging auxiliary wiring (bypass wiring) between the OLED element and each cathode contact in order to solve this shedding problem has been considered, this option is not suitable for a high definition display because auxiliary wiring must be arranged between each pixel.
Thus, the present invention attempts to provide an OLED display panel and manufacturing method thereof which can control shedding problems regardless of whether a panel is high definition or not.